[033/119] rtc: v3020: fix v3020_mmio_read_bit()

Greg KH
2009-12-07T00:32:45Z

[-- Attachment #1: rtc-v3020-fix-v3020_mmio_read_bit.patch --]
[-- Type: text/plain, Size: 1445 bytes --]

2.6.31-stable review patch. If anyone has any objections, please let us know.

------------------
From: Scott Valentine <svalentine@concentris-systems.com>

commit bcb3a1676b87effbdeffe8da5c44f63433d158d9 upstream.

v3020_mmio_read_bit() always returns 0 when left_shift > 7.

v3020_mmio_read_bit()'s return type is (unsigned char). The code returns
a value masked by (1 << left_shift) that is casted to the return type. If
left_shift is larger than 7, the cast will always result in a 0 return
value. The problem was discovered with left_shift = 16, and the included
patch corrects the problem.

The bug was introduced in the last (Apr 3 2009) commit of the file, kernel
versions 2.6.30 and later.

Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: Paul Gortmaker <p_gortmaker@yahoo.com>
Cc: Raphael Assenat <raph@8d.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
drivers/rtc/rtc-v3020.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/rtc/rtc-v3020.c
+++ b/drivers/rtc/rtc-v3020.c
@@ -96,7 +96,7 @@ static void v3020_mmio_write_bit(struct

static unsigned char v3020_mmio_read_bit(struct v3020 *chip)
{
- return readl(chip->ioaddress) & (1 << chip->leftshift);
+ return !!(readl(chip->ioaddress) & (1 << chip->leftshift));
}

static struct v3020_chip_ops v3020_mmio_ops = {